The present invention relates to a method of micro-processing of a nanometer level in which an atomic force microscopic technology is applied.
A micro-processing technology in a nanometer order is required for improvement of level and degree of integration of functions, and research and development regarding processing technologies such as local anodic oxidation or fine scratch processing using a scanning probe microscope (SPM) have been extensively carried out. Not only pursuit of possibility of micro-processing, but also an accurate shape or processing with high degree of accuracy is now increasingly required.
Recently, for example, correction of excessive-pattern defect of a photomask is performed by a fine scratch processing, in which processing is performed by scanning with a strong pushing force applied to a probe which is harder than material to be processed to achieve physical removal using a device based on an atomic force microscope (AFM) (for example, Y. Morikawa, H. Kokubo, M. Nishiguchi, N. Hayashi, R. White R. Bozak, and L. Terrill. Proc. of SPIE 5130 520-527(2003)). In order to correct the defect of the photomask, it is required not only that the fine defect is corrected with high degree of accuracy, but also that the position to be corrected has the same optical properties as the normal pattern and hence has the vertical cross-section same as the normal pattern.
In order to obtain the vertical cross-section by the AFM scratch processing, cutting is performed using a probe having a vertical cross-section. In this case, it is necessary to align the desired direction of vertical cross-section and the vertical cross-section of the probe. However, even when it is expected to be aligned as long as design is concerned, it is difficult to align them exactly due to the angle error at the time of mounting the probe and the angle error at the time of fixing a mask. When there are two or more desired directions of the vertical cross-section, the mask must be removed, rotated, and fixed again. After having re-fixed the mask, the position to be processed must be performed again from the beginning.
According to the method described. above, when there are two or more desired directions of vertical cross-section, a throughput of processing is significantly lowered. There is also a problem such that the processed shape is not necessarily the vertical cross-section due to the angle displacement of the vertical cross-section of the probe and due to the angle displacement of a sample.